1. Field of the Invention
The present invention relates to an expansion turbine stage for compressed gases, having a housing and a turbine rotor. The housing has flow guide channels for feeding the compressed gas to the turbine rotor. The turbine rotor is over-mounted and has centripetal flow through it. An out-flow diffuser enclosed by the housing follows the overhung turbine rotor to delay the cold expanded gas.
2. The Prior Art
Known expansion turbine stages having the characteristics described initially have drawbacks encountered in practice. At great temperature differences between the entering compressed gas and the expanded gas exiting from the turbine rotor, the effectiveness of these stages is reduced because of the heat exchange between these two gas streams, as the result of heat conduction in the turbine. In this connection, the heat transport into the out-flow diffuser from the housing is a particular problem. In this transport, the expanded gas stream is heated up, on the one hand and, at the same time, the compressed gas stream entering into the turbine rotor is cooled. The heat by-pass as described reduces the difference in enthalpy between the two streams. This reduction in turn reduces the technical work gained at the turbine rotor and thereby reduces the degree of effectiveness of the turbine. This problem is significant, in particular, in the case of very low, particularly cryogenic temperature ranges, in which turbine stages of the type being described are frequently used. For example, in the case of turbine stages in air separation plants, temperature differences of up to 150° K frequently occur between the entering stream and the exiting stream.